Method and apparatus for adaptively streaming content including plurality of chapters

ABSTRACT

A streaming method and apparatus, in which information regarding a plurality of chapters of content is inserted into a media presentation description that includes information regarding a plurality of media data generated by encoding the content so as to have different qualities, and then, streaming is performed based on the information.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication No. 61/315,500, filed on Mar. 19, 2010, U.S. ProvisionalPatent Application No. 61/362,805, filed on Jul. 9, 2010, and U.S.Provisional Patent Application No. 61/439,985, filed on Feb. 7, 2011, inthe U.S. Patent and Trademark Office, and Korean Patent Application No.10-2011-0021043, filed on Mar. 9, 2011 in the Korean IntellectualProperty Office, the disclosures of which are incorporated herein intheir entireties by reference.

BACKGROUND

1. Field

Exemplary embodiments relate to a streaming method and apparatus, andmore particularly, to a method and apparatus for adaptively streamingmedia data according to fluctuations in a streaming environment.

2. Description of the Related Art

Examples of a method of transmitting media data through a networkinclude a downloading method and a streaming method. In the streamingmethod, a server transmits media data in real time, and a clientreproduces the received media data in real time.

Unlike the downloading method that starts to reproduce media data aftertransmitting and receiving the media data, since the streaming methodtransmits and receives the media data through a logical channel setbetween the server and the client, and reproduces the media data in realtime, a method and apparatus for maintaining quality of service (QoS) inreproducing the media data by reflecting fluctuations in a streamingenvironment are required.

SUMMARY

Methods and apparatuses consistent with exemplary embodiments generallyrelate to adaptively adjusting and performing streaming, i.e.,adaptively transmitting and receiving media data according to astreaming environment.

An exemplary embodiment also provides a non-transitory computer readablerecording medium having recorded thereon a program which when executedby a computer performs the methods described herein.

According to an exemplary embodiment, there is provided a method ofreceiving media data, the method including receiving a file includinginformation regarding a plurality of media data generated by encodingcontent so as to have different qualities, from a server; and receivingat least one media data from among the plurality of media data, based onthe received file, wherein the file comprises information regarding aplurality of still images corresponding to a plurality of chapters ofthe content.

The receiving of the at least one media data may include receiving theplurality of still images, based on the received file; and receiving theat least one media data, starting from a chapter selected based on theplurality of still images.

The file may include a first tag including at least one from amonglocation information, resolution information, and compression typeinformation regarding the plurality of still images.

The first tag may have a same level as a second tag that identifies areproduction period of the content.

The first tag may have a same level as a third tag that is subject to asecond tag, which identifies a reproduction period of the content, andthat defines a plurality of media data to be reproduced in apredetermined reproduction period.

The first tag may further include information regarding intervalsbetween the plurality of still images.

According to another exemplary embodiment, there is provided a method oftransmitting media data, the method including transmitting a fileincluding information regarding a plurality of media data generated byencoding content so as to have different qualities, to a client; andtransmitting at least one media data from among the plurality of mediadata to the client, in response to a request based on the transmittedfile, received from the client, wherein the file comprises informationregarding a plurality of still images corresponding to a plurality ofchapters of the content.

The transmitting of the at least one media data to the client mayinclude transmitting the plurality of still images to the client, inresponse to the request based on the received file, received from theclient; and transmitting the at least one media data, starting from achapter selected by the client based on the plurality of still images.

According to another embodiment, there is provided an apparatus whichreceives media data, the apparatus including an information receivingunit which receives a file including information regarding a pluralityof media data generated by encoding content so as to have differentqualities, from a server; and a media data receiving unit which receivesat least one media data from among the plurality of media data, based onthe received file, wherein the file comprises information regarding aplurality of still images corresponding to a plurality of chapters ofthe content.

According to another embodiment, there is provided an apparatus whichtransmits media data, the apparatus including an informationtransmitting unit which transmits a file including information regardinga plurality of media data generated by encoding content so as to havedifferent qualities, to a client; and a media data transmitting unitwhich transmits at least one media data from among the plurality ofmedia data to the client, in response to a request based on thetransmitted file, received from the client, wherein the file comprisesinformation regarding a plurality of still images corresponding to aplurality of chapters of the content.

According to another embodiment, there is provided a non-transitorycomputer readable recording medium having stored thereon a computerreadable program which when executed by a computer performs the methodof receiving media data and/or the method of transmitting media data.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other features and advantages of the inventive conceptwill become more apparent by describing in detail exemplary embodimentsthereof with reference to the attached drawings in which:

FIG. 1 is a diagram of a streaming system according to an exemplaryembodiment;

FIGS. 2A and 2B are flowcharts for describing streaming methodsaccording to exemplary embodiments;

FIG. 3 is a schema of a file including information about content,according to an exemplary embodiment;

FIG. 4A illustrates information for defining a plurality of media data,according to an exemplary embodiment;

FIG. 4B illustrates information about a header of media data, accordingto an exemplary embodiment;

FIG. 4C illustrates information about at least one segment included ineach one of a plurality of media data, according to an exemplaryembodiment;

FIGS. 5A and 5B are flowcharts for describing streaming methodsaccording to other exemplary embodiments;

FIG. 6 is a schema of a file including information about content,according to another exemplary embodiment;

FIG. 7 illustrates information about content according to an exemplaryembodiment;

FIGS. 8A and 8B are schemas of a media presentation descriptionaccording to exemplary embodiments;

FIGS. 9A, 9B, 9C, 9D, 9E, 9F, 9G and 9H illustrate media presentationdescriptions according to exemplary embodiments;

FIGS. 10A, 10B and 10C each illustrate a plurality of media dataaccording to exemplary embodiments;

FIGS. 11A and 11B are flowcharts for describing streaming methodsaccording to exemplary embodiments;

FIGS. 12A, 12B and 12C each illustrate a plurality of media dataaccording to exemplary embodiments;

FIGS. 13A and 13B are flowcharts illustrating streaming methodsaccording to exemplary embodiments;

FIGS. 14A through 14H illustrate media presentation descriptionsaccording to other embodiments;

FIGS. 15A and 15B illustrate schemas of a chapter according to otherembodiments;

FIG. 16 illustrates information regarding a chapter, according to anembodiment;

FIG. 17 is a diagram illustrates the structure of chaptering data,according to an embodiment;

FIGS. 18A and 18B are flowcharts illustrating streaming methodsaccording to other embodiments;

FIG. 19 is a block diagram of a media data transmitting apparatus thatmay be included in the server of FIG. 1, according to an embodiment; and

FIG. 20 is a diagram of a media data receiving apparatus that may beincluded in the client of FIG. 1, according to an embodiment.

DETAILED DESCRIPTION

Hereinafter, exemplary embodiments will be described more fully withreference to the accompanying drawings, in which exemplary embodimentsare shown. Expressions such as “at least one of,” when preceding a listof elements, modify the entire list of elements and do not modify theindividual elements of the list.

FIG. 1 is a diagram of a streaming system 100 according to an exemplaryembodiment.

Referring to FIG. 1, the streaming system 100 according to an exemplaryembodiment includes an encoding device 110, a server 120, and a client130.

The encoding device 110 generates a plurality of media data about oneinput content by encoding the input content to have a plurality ofdifferent qualities. A streaming environment may change when the server120 streams media data to the client 130. For example, a bandwidth of anetwork 140 for streaming may be changed, or a hardware source that maybe used by the server 120 to transmit media data or by the client 130 toreceive media data may be changed.

Accordingly, the encoding device 110 encodes one content to havedifferent qualities for adaptive streaming according to a fluidicstreaming environment. One content may be encoded to have differentqualities by adjusting a factor, such as a bit rate, a samplingfrequency, resolution, or a frame rate. For example, a plurality ofmedia data in 500 Kbps, 1000 Kbps, and 2000 Kbps may be generated byencoding one image content in different resolutions.

The plurality of media data in different qualities are transmitted tothe server 120, and at this time, information about the content andinformation about each media data may also be transmitted to the server120. The information about the content may include, but is not limitedto, information about a title, a synopsis, a content identifier (ID),and a content uniform resource locator (URL) of the content as metadataof the content. The information about each media data may include aquality, a type, an ID, or the like of each media data, and will bedescribed in detail with reference to FIGS. 4A, 4B and 4C.

The client 130 receives at least one of the information about contentand information about each media data, and requests the server 120 forat least one of the plurality of media data, based on the received atleast one of the information about content and information about eachmedia data. The client 130 estimates a streaming environment, andselects at least one of the plurality of media data based on theestimated streaming environment. The at least one media data that maymaintain a suitable quality of service (QoS) in the estimated streamingenvironment may be selected. Then, the client 130 may transmit ahypertext transfer protocol (HTTP) request requesting the server 120 totransmit the selected at least one media data.

When a streaming environment is deteriorated and high quality media datais received but continuous reproduction of media data is not possible,low quality media data may be requested from among a plurality of mediadata. When a streaming environment is improved and high quality mediadata is received and continuous reproduction of media data is possible,the high quality media data may continue to be requested from among aplurality of media data.

The client 130 may request the server 120 to transmit another media datawhile receiving a predetermined media data. For example, the client 130,which requested and was receiving first media data that is of lowquality in a deteriorated streaming environment, may request the server120 to transmit second media data that is of a higher quality than thefirst media data as the streaming environment improves. According to aconventional streaming method, when the server 120 and the client 130sets a quality while initially setting a streaming channel, media datais continuously transmitted and received having the same quality.However, according to an exemplary embodiment, streaming that isadaptive to the streaming environment is possible since the client 130is able to request the second media data again even while receiving thefirst media data about the same content.

The client 130 may estimate a streaming environment by using any methodof estimating a streaming environment based on the bandwidth of thenetwork 140 or the hardware resource that may be used by the server 120or the client 130. For example, the client 130 may estimate thestreaming environment based on a time stamp and a bit error rate (BER)of received media data. The streaming environment may be determined tobe deteriorated when media data is received slower than a reproductionspeed by checking time stamps of the received media data. Alternatively,the streaming environment may be determined to be deteriorated when BERsof the received media data are increased.

When the client 130 requests the server 120 to transmit at least one ofthe media data according to the streaming environment, the server 120transmits requested media data to the client 130. The server 120 maytransmit the requested media data to the client 130 as an HTTP responseto the HTTP request.

Each media data may include at least one of a plurality of segmentsgenerated by encoding content in different qualities and dividing theencoded content. In other words, each media data generated by encodingthe content by the encoding device 110 may include at least one segmentdivided based on time. The server 120 transmits the content by dividingthe content into the plurality of segments and respectively transmittingthe plurality of segments, instead of encoding the content in one streamand continuously transmitting the content. The plurality of segments maybe generated by dividing the content into predetermined time units, suchas units of 10 or 20 seconds. The time that is the basis for dividingthe content may be set based on a group of pictures (GOP). Media datacorresponding to pictures of one or more GOPs may be set as one segment.

For example, when content is streamed having two qualities, the firstmedia data may include at least one segment generated by encoding thecontent to have a first quality and dividing the encoded content basedon time, and the second media data may include at least one segmentgenerated by encoding the content to have a second quality and dividingthe encoded content based on time.

The adaptive streaming is possible by dividing each media data based ontime. For example, when streaming starts, the server 120 transmits asegment corresponding to 0 to 20 seconds of the first media data that isof low quality. Then, when it is determined that the streamingenvironment is improved after 20 seconds and the client 130 requestsmedia data that is of higher quality, the server 120 may transmit asegment corresponding to 20 to 40 seconds of the second media data thatis of the higher quality. Since media data is divided into a pluralityof segments based on time, segments of different media data may betransmitted according to a streaming environment, even during streaming.

FIG. 2A is a flowchart for describing a streaming method according to anexemplary embodiment.

Referring to FIG. 2A, the client 130 transmits a request to the server120 to transmit information about predetermined content, in operation210. When a user of the client 130 selects the predetermined contentfrom a user interface displayed on a screen of the client 130, theclient 130 requests the server 120 to transmit information about theselected content. The client 130 may transmit an HTTP request requestingthe server 120 to transmit information about predetermined content.

Upon receiving the request from the client 130, the server 120 transmitsthe information about the predetermined content to the client 130. Theserver 120 may transmit the information about the predetermined contentas an HTTP response to the HTTP request to the client 130. Theinformation about the predetermined content may be a content accessdescriptor (CAD) according to an open IPTV forum (OIPF) standard. Theinformation about the predetermined content will now be described indetail with reference to FIG. 3.

FIG. 3 is a schema of a file including information about content,according to an exemplary embodiment. The file may be a CAD, and may bean eXtensible Markup Language (XML) file. A tag and an attribute areseparately described, but it is understood that according to anexemplary embodiment an item defined by a tag can be defined by anattribute or an item defined by an attribute can be defined by a tag.

Referring to FIG. 3, the information about content may include “Title”,“Synopsis”, “OriginSite”, and “ContentURL” tags.

Since conventional streaming of media data generates one media data byencoding one content to have a predetermined quality, conventionalinformation (specifically, CAD according to OIPF) about content does notinclude information about a plurality of media data generated byencoding the content to have different qualities.

However, the information about content, according to the presentexemplary embodiment, includes information about a plurality of mediadata generated by encoding one content to have different qualities, andcorresponds to “Tracks”, “RefData”, and “Fragments” tags in FIG. 3.

FIG. 4A illustrates information for defining a plurality of media data,according to an exemplary embodiment.

Referring to FIG. 4A, a “Tracks” tag is information for classifying aplurality of media data generated by encoding content to have differentqualities. The “Tracks” tag includes an “ID” attribute, a “Type”attribute, and a “BitRate” attribute assigned to each media data.

The “ID” attribute defines identifiers sequentially given to theplurality of media data, and the “Type” attribute defines whether mediadata corresponds to audio data, video data, video/audio data, orsubtitle data. When the “Type” attribute is “Packed”, the media data isvideo/audio data, and when the “Type” attribute is “Video”, the mediadata is video data. The “BitRate” attribute defines a bit rate used toencode the media data.

FIG. 4B illustrates information about a header of media data, accordingto an exemplary embodiment.

Referring to FIG. 4B, a “RefData” tag includes a “Type” attribute and an“ID” attribute. The “Type” attribute defines a media format of a header.For example, when the “Type” attribute is “HEAD-TS”, the header is aheader of a transport stream format. The “ID” attribute defines a mediadata of a header. When the “ID” attribute is “1”, the header is a headerof media data having a media data ID of “1”. Also, the “RefData” tagincludes information pointing to a header, and an “URL” tag defines alocation of a header, i.e., a URL of a header.

The “RefData” tag is a selective element. The “RefData” tag is includedin information about content only when a header is separated from mediadata and exists as a separate file, and may not be included in theinformation about content when the header is combined with the mediadata.

FIG. 4C illustrates information about at least one segment included ineach of a plurality of media data, according to an exemplary embodiment.

Referring to FIG. 4C, a “Fragment” tag, which is a sub tag of a“Fragments” tag, includes the information about at least one segmentincluded in each of the plurality of media data.

The “Fragments” tag includes a “NextFragmentsXMLURL” attribute. Whenfollowing content is continuously streamed after streaming of onecontent is completed like in the case of live streaming, the followingcontent may be seamlessly streamed only when the client 130 is aware ofinformation about the following content. Accordingly, the “Fragments”tag defines the information about the following content as the“NextFragmentsXMLURL” attribute. URLs of the plurality of media datawith respect to the following content may be defined as the“NextFragmentsXMLURL” attribute.

The “Fragment” tag includes information about at least one segment ofcurrent content. Referring to FIG. 4C, URL information of “slice1-1.as”constituting a first segment generated by encoding content in a firstquality as first media data is defined by a “URL” tag, and an ID of acorresponding header is defined by a “RefPointer” tag. Also, a startingtime of the first segment is defined by a “StartTime” attribute, and aduration time of each segment is defined by a “Duration” attribute. Aquality of the first media data is defined by a “BitRate” attribute.

In FIG. 4C, the “Fragments” tag shows each media data including only onesegment. However, as described above with reference to FIG. 1, it isunderstood that according to an exemplary embodiment, when each mediadata is divided into a plurality of segments, one “Fragments” tag mayinclude information about at least two segments.

Referring back to FIG. 2A, the client 130 requests the server 120 totransmit at least one of the plurality of media data, in operation 220.The plurality of media data are generated by encoding one content tohave different qualities. The client 130 selects at least one media dataencoded to have a quality suitable for a streaming environment fromamong the plurality of media data, and requests the server 120 for theselected at least one media data. The client 130 may transmit an HTTPrequest to the server 120 based on information about the plurality ofmedia data, which is included in the information about the content.

As described with reference to FIG. 4C, the information about thecontent may include a “Fragments” tag. Accordingly, the client 130requests the server 120 to transmit selected media data based on URLinformation included in the “Fragments” tag.

The server 120 transmits the media data according to the request of theclient 130. The server 120 may transmit at least one segment of therequested media data to the client 130. The server 120 may transmitmedia data requested as an HTTP response with respect to an HTTP requestto the client 130.

FIG. 2B is a flowchart for describing a streaming method according toanother exemplary embodiment. FIG. 2B illustrates the streaming methodwhen a header exists as a separate file from media data.

Referring to FIG. 2B, the client 130 requests the server 120 to transmitinformation about predetermined content, in operation 212, and theserver 120 transmits the information about content. Operation 212corresponds to operation 210 of FIG. 2A. The information about contentincluding the “RefData” tag described above with reference to FIG. 4B isreceived.

In operation 222, the client 130 requests a header of selected mediadata from among a plurality of media data, based on the informationabout content received in operation 212. At least one media datasuitable for a streaming environment is selected from among theplurality of media data based on the information about content receivedin operation 212, and a header of the selected at least one media datais requested. The header of the selected at least one media data isrequested by referring to the “RefData” tag included in the informationabout content received in operation 212.

The server 120 transmits the requested header to the client 130. Aheader file may be transmitted to the client 130, and may be an XMLfile.

In operation 232, the client 130 requests the server 120 to transmitselected media data based on the information about content received inoperation 212 and the header received in operation 222. The client 130requests the server 120 to transmit at least one segment generated bydividing media data based on time, and the server 120 transmits therequested at least one segment to the client 130.

FIG. 5A is a flowchart for describing a streaming method according toanother exemplary embodiment.

Referring to FIG. 5A, the client 130 requests the server 120 to transmitinformation about predetermined content, in operation 510, and theserver 120 transmits the information about content. The client 130transmits an HTTP request for requesting the server 120 to transmit theinformation about content, and receives the information about content asan HTTP response to the HTTP request. The information about content maybe an XML file. The information about content received by the client 130in operation 510 is different from the information about contentreceived by client 130 in operation 210 of FIG. 2, and the differencewill now be described with reference to FIGS. 6 and 7.

FIG. 6 is a schema of a file including information about content,according to another exemplary embodiment.

Referring to FIG. 6, the information about content according to thepresent exemplary embodiment may include “Title”, “Synopsis”,“OriginSite”, and “ContentURL” tags like FIG. 3.

However, in FIG. 3, the information about content includes theinformation about the plurality of media data by including the “Tracks”,“RefData”, and “Fragments” tags, whereas in FIG. 6, instead of includingthe information about the plurality of media data, the information aboutcontent only defines a URL of a file (hereinafter, referred to as a“media presentation description”) including the information about theplurality of media data. The “ContentURL” tag may define the URL of themedia presentation description.

Compatibility with various media data formats may be maintained whileperforming streaming that is adaptive to a streaming environment byinserting the URL of the media presentation description into theinformation about content as shown in FIG. 6, without largely changingconventional schema of the file containing the information aboutcontent.

As shown in FIG. 6, the information about content may only includeinformation related to the streaming method, and not include theinformation about the plurality of media data. In other words, the“ContentURL” tag may include a “MediaFormat” attribute defining a formatof media data used during streaming, and a “MIMEType” attribute defininga type of media data.

Specifically, the “ContentURL” tag may include a “TransferType”attribute defining a service to which streaming of content is related.The “TransferType” attribute may define whether the streaming of contentis related to a Content on Delivery (CoD) service, a live service, anadaptive streaming live service, or an adaptive streaming CoD service.

FIG. 7 illustrates information about content according to an exemplaryembodiment. FIG. 7 may be a CAD according to the OIPF standard.

Referring to FIG. 7, the information about content generated accordingto the schema of FIG. 6 may define a URL of a media presentationdescription in a “ContentURL” tag.http://asexample.com/vod/movies/18888/Meta/MainMeta.xml is the URL ofthe media presentation description. Also, as described with reference toFIG. 6, the “MediaFormat” attribute, the “MIMEType” attribute, and the“TransferType” attribute may be defined in the “ContentURL” tag.

Referring back to FIG. 5A, in operation 520, the client 130 requests theserver 120 for the information about the plurality of media data, basedon the information about content received in operation 510. The client130 may request a media presentation description to the server 120through an HTTP request, and may receive the media presentationdescription as an HTTP response.

The information about content received by the client 130 from the server120 in operation 510 may include the URL of the media presentationdescription as described with reference to FIGS. 6 and 7, and thus theclient 130 requests and receives the media presentation description fromthe server 120 by referring to the “ContentURL” tag of the informationabout content. The media presentation description will now be describedin detail with reference to FIGS. 8A and 8B, and FIGS. 9A, 9B, 9C, 9D,9E, 9F, 9G and 9H.

FIGS. 8A and 8B are schemas of a media presentation descriptionaccording to exemplary embodiments. The media presentation descriptionmay comply with the OIPF standard.

Referring to FIG. 8A, the media presentation description according tothe present exemplary embodiment includes a template tag about URLs of aplurality of media data, a tag for defining a location of a header, atag for defining to which service the streaming is related to, a tag fordefining a container format of media data, and a tag for defining theplurality of media data.

An “urlTemplate” tag defines a common portion of the URLs of theplurality of media data. For example, if“http://example.com/vod/movie/18888/Track/{TrackID}/Segments/{SegmentID}”is a URL template, a URL of media data may be defined by respectivelysubstituting an ID of each media data and an ID of at least one segmentincluded in each media data for “TrackID” and “SegmentID”.

A “headerUrl” tag corresponds to the “RefData” tag described withreference to FIG. 4B. In other words, the “headerUrl” tag defines URLsof headers of the plurality of media data.

An “is Live” tag defines a service related to streaming. For example,when the “is Live” tag is defined as “Live”, the streaming is related toa live service, and when the “is Live” tag is defined as “CoD”, thestreaming is related to a CoD service.

A “contentType” tag defines a container format of media data used duringstreaming. The “contentType” tag may indicate whether the containerformat is an MP4 format or an MPEG2-TS format. The container format isan MP4 format or an MPEG2-TS format herein, However, though it isunderstood that according to an exemplary embodiment the containerformat is not limited thereto, and any container format for transmittingmedia data may be used. For example, the “contentType” tag may definethat the container format complies with an MPEG Media Transport (MMT)standard.

A “Stream” tag is generated for each media data and defines each mediadata. In order to define each media data generated by encoding onecontent to have different qualities, the “Stream” tag includes a“streamName” attribute, a “type” attribute, a “bitrate” attribute, a“startTime” attribute, a “firstIntervalNum” attribute, a “duration”attribute, and an “intervalCount” attribute.

The “streamName” attribute defines a name of media data, and may be anID of media data. The “type” attribute defines a type of media data,wherein it is defined whether the media data is audio data, video data,or audio/video data. When media data only includes data about an I-framefor a trick play, such information may be defined in the “type”attribute.

The “bitrate” attribute defines a bit rate of media data, the“startTime” attribute defines a time stamp for specifying a startingtime of media data, and the “firstIntervalNum” attribute defines anumber of a segment that initially starts.

The “duration” attribute defines a duration time of a segment includedin media data, and the “intervalCount” attribute defines a total numberof at least one segment included in media data.

The “Segment” tag is a sub tag of the “Stream” tag, and as describedabove, when media data includes at least one segment generated byencoding content in a predetermined quality and dividing the encodedcontent based on time, each of the at least one segment is defined.

The “IntNum” attribute defines a number of a segment, and the“StartTime” tag defines a starting time of a corresponding segment. The“Duration” tag defines a duration time of a corresponding segment, andthe “url” defines a URL of a corresponding segment.

The “Segment” tag is a selective tag, and may not be included in themedia presentation description if the information about at least onesegment included in the media data can be inferred from other attributesof the “Stream” tag. In other words, when content of the “Segment” tagcan be inferred from the “startTime”, “firstIntervalNum”, “duration”,and “intervalCount” attributes defined in the “Stream” tag, the“Segment” tag may not be included in the media presentation description.Also, a “url” attribute of the “Segment” tag may not be required if apredetermined template is defined in the “urlTemplate”, and the URLs ofsegments are inferred by substituting each ID of the plurality of mediadata and an ID of at least one segment included in each media data withthe defined predetermined template.

However, on the other hand, attributes of the “Segment” tag areseparately defined for each segment, if the attributes of the “Segment”tag cannot be inferred from other attributes of the “Stream” tag. Theattributes of the “Segment” tag may not be inferred if duration times ofsegments are different. When duration times are different, the durationtimes of segments included in media data cannot be inferred from theattributes of the “Stream” tag, and thus the duration times of thesegments may be each set by using a “duration” attribute of the“Segment” tag. When the duration times of the segments are different,starting times of continuous segments are also different. For example,when a duration time of a first segment of first media data is differentfrom a duration time of a second segment of the first media data, astarting time of the second segment and a starting time of a thirdsegment cannot be inferred from the “Stream” tag. Accordingly, astarting time of each segment may be defined by a “startTime” attribute.

The duration times and/or starting times may be defined by using a subtag of the “Segment” tag, instead of using the “duration” attribute andthe “startTime” attribute of the “Segment” tag. For example, a “Url” tagconstituting a sub tag of the “Segment” tag may be set, and a durationtime may be defined as an attribute of the “Url” tag, such as“<Url=www.example.com/˜/segment.ts,duration=10/>”.

According to another exemplary embodiment, duration time may be definedbased on a difference between duration times of continuous segments. Anupper tag may define a default duration time, and the “Url” tagconstituting the sub tag may define only a difference between thedefault duration time and an actual duration time for each segment. Asdescribed above, the “Url” tag constituting the sub tag of the “Segment”tag may be defined as“<Url=www.example.com/˜/segment.ts,duration=difference/>”. “Difference”denotes a difference between the default duration time and the actualduration time.

When a default duration time of a corresponding segment is defined to be10 minutes by using the “Stream” tag or the “Segment” tag, and the “Url”tag constituting the sub tag is defined to be“<Url=www.example.com/˜/segment.ts,duration=2/>”, a duration time of thecorresponding segment may be defined to be 10+2=12 minutes.

Referring to FIG. 8B, the media presentation description according toanother exemplary embodiment may further include a “nextManifestURL”tag. As described above, when following content is continuously streamedafter streaming of one content is completed, such as in the case of livestreaming or advertisement insertion, the client 130 requires topre-know information about the following content so as to stream thefollowing content seamlessly. Accordingly, a URL of a media presentationdescription of the following content to be streamed after currentcontent may be defined by the “nextManifestURL” tag.

FIGS. 9A, 9B, 9C, 9D, 9E, 9F, 9G and 9H illustrate media presentationdescriptions according to exemplary embodiments.

Referring to FIG. 9A, the media presentation description according to anexemplary embodiment includes a “URLTemplate” tag, a “RefDataURL” tag,and a plurality of tags respectively defining a plurality of media data.

The “URLTemplate” tag and the “RefDataURL” tag of FIG. 9A respectivelycorrespond to the “urlTemplate” tag and the “RefDataURL” tag of FIGS. 8Aand 8B.

An “ID” attribute, a “Type” attribute, a “BitRate” attribute, a“StartTime” attribute, a “SegmentDuration” attribute, a “SegmentStartID”attribute, and a “SegmentCount” attribute of FIG. 9A respectivelycorrespond to the “streamName” attribute, the “type” attribute, the“bitrate” attribute, the “startTime” attribute, the “duration” attributeof the “Stream” tag, the “firstIntervalNum” attribute of the “Stream”tag, and the “intervalCount” attribute of FIGS. 8A and 8B.

The media presentation description of FIG. 9A includes information aboutthree video data generated by encoding content to have differentqualities, information about one audio data, and information about mediadata generated by encoding only I-frames for a trick play.

Referring to FIG. 9B, the media presentation description according to anexemplary embodiment further includes a “NextAdaptiveControlURL” tag.The “NextAdaptiveControlURL” tag corresponds to the “nextManifestURL”tag of FIG. 8B. Accordingly, a URL of a media presentation descriptionof following content to be reproduced after current content may bedefined by the “NextAdaptiveControlURL” tag.

FIG. 9C shows a media presentation description of the following content,when the URL of the media presentation description of the followingcontent to be reproduced after the current content is defined by the“NextAdaptiveControlURL” tag of FIG. 9B. Comparing the mediapresentation descriptions of FIGS. 9B and 9C, a “StartTime” attribute isdifferent from the media presentation description of the current contentof FIG. 9B, since the media presentation description of FIG. 9C is forthe following content.

FIGS. 9D and 9E illustrate media presentation descriptions forselectively controlling high quality video reproduction that a user wantto perform. FIG. 9D illustrates the media presentation description whena plurality of media data are generated by encoding one content to have5 different qualities. Here, the media presentation descriptions ofFIGS. 9D and 9E are different in a tag including information about videoencoded to have high quality, i.e., a “StartTime” attribute and a“SegmentCount” attribute of media data having an “ID” attribute of “5”.

The server 120 selectively transmits the media presentation descriptionof FIG. 9D or the media presentation description of FIG. 9E according toa user rating of the client 130. When the user rating of the client 130is high (for example, when the client 130 is a paid user), the mediapresentation description of FIG. 9D is transmitted so that high qualityvideo is freely reproduced, and when the user rating of the client 130is low (for example, when the client 130 is a free user), the mediapresentation description of FIG. 9E is transmitted so that segmentsdefined by the “SegmentCount” attribute are reproduced from a timedefined by the “StartTime” attribute in high quality video.

FIG. 9F illustrates a media presentation description when anadvertisement is inserted into content. Referring to FIG. 9F, the mediapresentation description may include information about advertisementcontent and main content, which have different “StartTime” attributes.The media presentation description may include information aboutadvertisement content, which is reproduced from “00:00:00” to “00:02:00”at a bit rate of “500000”, and information about main content, which isreproduced from “00:02:00” at bit rates of “1000000”, “2000000”,“3000000”, or “4000000”. The media presentation description of FIG. 9Fmay be transmitted from the server 120 to the client 130 if the server120 provides the advertisement content to the client 130 by encoding theadvertisement content to have one bit rate, and provides the maincontent, which has a different “StartTime” attribute from theadvertisement content, to the client 130 by encoding the main content infour different bit rates.

FIG. 9G illustrates a media presentation description includinginformation about advertisement content, according to an exemplaryembodiment. A server for providing main content and a server forproviding advertisement content may be different. In other words, whenthe client 130 receives the main content from the server 120 of FIG. 5Aand receives the advertisement content from a server other than theserver 120, the media presentation description of FIG. 9G may include aURL of the advertisement content. As shown in FIG. 9G, the mediapresentation description may include the URL of the advertisementcontent that is encoded to have one quality.

FIG. 9H illustrates a media presentation description including languageand subtitle information, according to an exemplary embodiment.Referring to FIG. 9H, audio data may include information about multiplelanguages. The media presentation description may include informationabout audio data of multiple languages, wherein an “ID” attribute is “4”or “5”, or information about subtitles of multiple languages, whereinthe “ID” attribute is “6” or “7”.

Since not only the audio data, but also the subtitle may be divided intoa plurality of segments according to time, the audio data and thesubtitle may be changed to audio data and a subtitle of another languageduring streaming.

Referring back to FIG. 5A, the client 130 requests the server 120 totransmit at least one of the plurality of media data, in operation 530.The client 130 selects at least one media data that is encoded to have aquality suitable for the streaming environment by referring to theinformation about the plurality of media data, and requests the server120 for the selected at least one media data. The client 130 maytransmit an HTTP request for requesting the server 120 to transmit apredetermined media data. The server 120 transmits the media dataaccording to the request of the client 130. Alternatively, the servermay transmit at least one segment generated by encoding content to havea predetermined quality and dividing the encoded content based on time,to the client 130. The server 120 may transmit the requested media datato the client 130 as an HTTP response to the HTTP request.

FIG. 5B is a flowchart for describing a streaming method according toanother exemplary embodiment.

Referring to FIG. 5B, the client 130 requests the server 120 to transmitinformation about predetermined content, in operation 512, and receivesthe information about predetermined content from the server 120. Theclient 130 may transmit an HTTP request for requesting the server 120 totransmit the information about predetermined content, and receive theinformation about predetermined content as an HTTP response to the HTTPrequest. The information about predetermined content may be included inan XML file.

In operation 522, the client 130 requests the server 120 to transmitinformation about a plurality of media data based on the informationabout predetermined content received in operation 512. The client 130may request the server 120 for a media presentation description throughthe HTTP request, and receive the media presentation description as theHTTP response.

In operation 532, the client 130 requests a header of media dataselected based on the information about a plurality of media datareceived in operation 522. At least one media data that is suitable to astreaming environment is selected from among the plurality of media databased on the information about the plurality of media data received inoperation 522, and a header of the selected at least one media data isrequested. The header of the selected at least one media data isrequested by referring to the information about the plurality of mediadata received in operation 522. The server 120 transmits a file of theheader of the selected at least one media data to the client 130 inresponse to the request of the client 130.

In operation 542, the client 130 requests the server 120 to transmitselected media data based on the information about the plurality ofmedia data received in operation 522, and the header received inoperation 532. The client 130 requests the server 120 to transmit atleast one segment generated by encoding content to have a predeterminedquality and dividing the encoded content based on time, and the server120 transmits the requested at least one segment to the client 130.

FIGS. 10A, 10B and 10C each illustrate a plurality of media dataaccording to exemplary embodiments. FIGS. 10A, 10B and 10C eachillustrate the plurality of media data included in the server 120 toperform the streaming methods according to FIGS. 5A and 5B.

Referring to FIG. 10A, the server 120 may include a plurality of mediadata 1010 through 1030 generated by encoding one content to have aplurality of different qualities, for streaming that is adaptive to astreaming environment. “Track1” through “TrackN” denote the plurality ofmedia data 1010 through 1030. Also, each of the plurality of media data1010 through 1030 may include at least one segment generated by dividingeach of the plurality of media data 1010 through 1030 based on time.“Slice1-1.as”, “Slice1-2.as”, “Slice1-3.as”, “Slice2-1.as”,“Slice2-2.as”, “Slice2-3.as”, “SliceN-1.as”, “SliceN-2.as”, and“SliceN-3.as” denote at least one segment.

The server 120 may include information 1040 required for the client 130to access the plurality of media data 1010 through 1030. The server 120may include a “CadMeta.xml” file as information about content, a“MainMeta.xml” file as information about the plurality of media data1010 through 1030, and a “Head1.ref” file, a “Head2.ref” file, etc. asheader files of the plurality of media data 1010 through 1030. Here, the“Head1.ref” file may be a header file of the “Track1”, and the“Head2.ref” file may be a header file of the “Track2”.

The “CadMeta.xml” file may be a CAD file according to the OIPF standard,and the “MainMeta.xml” file may be the media presentation descriptiondescribed above. Also, the “Head1.ref” and “Head2.ref” files areselective elements, and may not exist when headers are included in theplurality of media data 1010 through 1030.

Referring to FIG. 10B, information 1042 required for the client 130 toaccess the plurality of media data 1010 through 1030 may further includea “NextMeta.xml” file. As described above, the “NextMeta.xml” file maybe a media presentation description of a following content to bereproduced after current content. As described above, the mediapresentation description of the current content, i.e., the“MainMeta.xml” file, includes the URL of the media presentationdescription of the following content, and thus the client 130 may accessthe “NextMeta.xml” file based on the “MainMeta.xml” file.

Referring to FIG. 10C, header files of the plurality of media data 1010through 1030 may exist in one header file 1050. Instead of existing foreach of the plurality of media data 1010 through 1030, the header filesmay exist as one header file 1050 and may be included in information1044 required to access the plurality of media data 1010 through 1030.

For example, when each of the plurality of media data 1010 through 1030corresponds to an elementary stream, e.g., an elementary streamaccording to the MPEG-2 standard, each of the header files of theplurality of media data 1010 through 1030 may be the header file 1050including a program association table (PAT) and a program map table(PMT). At least one of the PAT and the PMT may be separated from theplurality of media data 1010 through 1030 to prepare the header file1050, and the media presentation description may include informationpointing to the header file 1050. The information pointing to the headerfile 1050 may be URL information of the header file 1050 or informationfor specifying a packet including the header file 1050 in a MPEG-2transport stream (TS). The header file 1050 including at least one ofthe PAT and the PMT is an initialization segment, and may be transmittedto the client 130 before segments including payload data, so as toinitiate reproduction of the plurality of media data 1010 through 1030.

Referring back to operation 532 of FIG. 5B, the client 130 may obtainthe information pointing to the header file 1050 by referring to themedia presentation description, and may request the header file 1050based on the information pointing the header file 1050. After requestingand receiving the header file 1050 based on the information pointing tothe header file 1050, at least one of the plurality of media data 1010through 1030 is selected based on at least one of the PAT and the PMTincluded in the header file 1050, and the selected at least one mediadata is requested from the server 120. The PAT and the PMT may beseparated as the header file 1050 or included in the plurality of mediadata 1010 through 1030, but may include an entire list of elementarystreams included in the plurality of media data 1010 through 1030regardless of locations of the PAT and the PMT.

According to MPEG-2, packet IDs (PIDs) defined in the PAT and the PMTare different according to elementary streams. Accordingly, PIDsassigned to each of the plurality of media data 1010 through 1030 may bedifferent. Alternatively, according to another exemplary embodiment,since the plurality of media data 1010 through 1030, generated byencoding one content to have different qualities, are elementary streamsof the same content, the same PID may be employed.

When the plurality of media data 1010 through 1030 correspond to aplurality of elementary streams according to MPEG-2, each of segmentsincluded in the plurality of media data 1010 through 1030 may include atleast one continuous packetized elementary stream (PES). However, onePES may be included in only one segment from among the segments. Inother words, one PES may not be included in two different segments.

Since a plurality of media data are generated by encoding one content tohave different qualities, presentation time stamps (PTSs) and/ordecoding time stamps (DTSs) included in PESs of the plurality of mediadata may be aligned according to reproduction times. In other words, ifan initial PES of first media data and an initial PES of second mediadata are content reproduced at the same time, a PTS and/or a DTS may beequally set.

Further, when the second media data is reproduced while reproducing thefirst media data by changing media data according to the streamingenvironment, the PTSs and/or the DTSs may be continuously aligned sothat the first and second media data are continuously reproduced. Inother words, when the second media data is reproduced while reproducingthe first media data, by changing media data, the PTS and/or the DTS ofthe last PES before the changing of the media data, and the PTS and/orthe DTS of the first PES after the changing of the media data, may becontinuously set.

The PTS and/or the DTS define a time stamp of video data. Accordingly,time stamps of the plurality of media data with respect to video dataare aligned according to the reproduction times of the plurality ofmedia data as described above. Such alignment of the time stamps basedon the reproduction times may be equally applied to audio data. In otherwords, like the time stamps of the plurality of media data with respectto the video data, time stamps of the pieces media data with respect tothe audio data may also be aligned according to the reproduction timesfor adaptive streaming.

FIG. 11A is a flowchart for describing a streaming method according toanother exemplary embodiment.

Referring to FIG. 11A, the client 130 requests information about aplurality of media data to the server 120, in operation 1110. The client130 may request a media presentation description from the server 120 viaan HTTP request, and may receive the media presentation description asan HTTP response. The client 130 requests the server 120 for andreceives the information about the plurality of media data generated byencoding one content to have a plurality of different qualities, so asto perform streaming that is adaptive to a streaming environment. Thestreaming method of FIG. 11A is different from the streaming method ofFIG. 5A as the information about the plurality of media data isrequested and received without requesting and receiving informationabout content.

In operation 1120, the client 130 requests the server 120 to transmit atleast one of the plurality of media data. The client 130 selects andrequests at least one media data that is encoded to have a qualitysuitable for the streaming environment by referring to the informationabout the plurality of media data, and receives the requested at leastone media data from the server 120.

FIG. 11B is a flowchart for describing a streaming method according toanother exemplary embodiment.

Referring to FIG. 11B, the client 130 requests the server 120 totransmit information about a plurality of media data and receives theinformation about the plurality of media data from the server 120 inresponse to the request, in operation 1112. The client 130 may requestthe server 120 for a media presentation description through an HTTPrequest, and receive the media presentation description as an HTTPresponse.

In operation 1122, the client 130 requests a header of selected mediadata based on the information about the plurality of media data receivedin operation 1112. The client 130 requests the header of media dataselected according to a streaming environment by referring to theinformation about the plurality of media data received in operation1112. In response to the request, the server 120 transmits a fileincluding the header of the selected media data to the client 130.

In operation 1132, the client 130 requests the server 120 to transmitthe media data selected based on the information about the plurality ofmedia data received in operation 1112, and the header received inoperation 1122. The client 130 requests the server 120 to transmit atleast one segment generated by encoding content in a predeterminedquality and dividing the encoded content based on time, and the server120 transmits the requested at least one segment to the client 130.

FIGS. 12A, 12 B and 12C each illustrate a plurality of media dataaccording to other exemplary embodiments. FIGS. 12A and 12B eachillustrate the plurality of media data included in the server 120, whichare used to perform the streaming methods of FIGS. 11A and 11B.

Referring to FIG. 12A, the server 120 may include the plurality of mediadata 1010 through 1030 generated by encoding one content to have theplurality of different qualities for streaming that is adaptive to astreaming environment, as shown in FIG. 10A.

Here, the plurality of media data 1010 through 1030 of FIG. 12A isdifferent from the plurality of media data 1010 through 1030 of FIG. 10Ain information 1240 required for the client 130 to access the pluralityof media data 1010 through 1030, wherein the server 120 only includesinformation about the plurality of media data 1010 through 1030 and notinformation about content, unlike the exemplary embodiment of FIG. 10A.Here, the client 130 may receive the information about content fromanother entity instead of the server 120, and access the plurality ofmedia data 1010 through 1030 included in the server 120 based on thereceived information about content.

Referring to FIG. 12B, information 1242 required for the client 130 toaccess the plurality of media data 1010 through 1030 may be prepared byfurther including a “NextMeta.xml” file to the information 1240 of FIG.12A.

Referring to FIG. 12C, the header files of the plurality of media data1010 through 1030 may exist in one header file 1250. The header files donot exist for each of the plurality of media data 1010 through 1030, butmay be included in information 1244 required to access the plurality ofmedia data 1010 through 1030, as one header file 1250. The header file1250 corresponds to the header file 1050 of FIG. 10C.

FIG. 13A is a flowchart illustrating a streaming method according toanother embodiment. Referring to FIG. 13A, in operation 1310, a client130 requests a server 120 to provide information regarding desiredcontent, and receives the information regarding the desired content fromthe server 120. For this end, the client 130 may transmit an HTTPrequest for the information regarding the desired content to the server120 and receive the information regarding the desired content from theserver 120 according to the HTTP response. An XML file containing theinformation regarding the desired content may be received. Theinformation regarding the desired content may include the URL of a mediapresentation description as described above in detail with reference toFIGS. 6 and 7.

In operation 1320, the client 130 requests the server 120 to provideinformation regarding a plurality of media data, based on theinformation regarding the desired content received in operation 1310.The client 130 may transmit an HTTP request for a media presentationdescription to the server 120 and receive the media presentationdescription from the server 120 according to the HTTP response.

The media presentation description that the client 130 receives inoperation 1320 may be one of the media presentation descriptionsdescribed above in detail with reference to FIGS. 8A, 8B, and 9A to 9Gand may contain information regarding a plurality of chapters of thecontent. The plurality of chapters of the content will now be describedin detail with reference to FIGS. 14A to 14H.

FIGS. 14A through 14H illustrate media presentation descriptionsaccording to other embodiments. Referring to FIG. 14A, a mediapresentation description according to another embodiment includes“Period” tags that are subject to a “MPD” tag (an uppermost tag) andidentify reproduction periods of content that is being streamed,respectively. Each of the “Period” tags includes an “Representation” taghaving information regarding a plurality of media data that are to bestreamed in a corresponding reproduction period. Also, each of the“Representation” tags may include a “SegmenInfo” tag having informationregarding a plurality of segments divided from one media data accordingto time.

The media presentation description further includes a “Chaptering” taghaving information regarding a plurality of chapters of the content thatis being streamed. The content may include the plurality of chaptersclassified according to a scene, a story, or time. The informationregarding the plurality of chapters is defined with the “Chaptering”tag. Information regarding at least one of a still image and textsrelated to a particular chapter may be information regarding thechapter.

The “Chaptering” tag may include at least one attribute defining a stillimage corresponding to the plurality of chapters. The format, URL, andtime intervals of at least one still image are defined with a “mimeType”attribute, a “URL” attribute, and an “ImageInterval” attribute. Theresolution of the at least one still image is defined with a “height”attribute and a “width” attribute. The “height” attribute and the“width” attribute define the horizontal and vertical sizes of the atleast one still image, i.e., the resolution of the at least one stillimage. Also, a compression type of the at least one still image isdefined with a “compressiontype” attribute.

The “URL” attribute of the “Chaptering” tag may be a template, similarto the “URL” attribute of the media presentation description describedabove. The template is a common part of the URLs of a plurality of stillimages and may be defined with the “URL” attribute.

Referring to FIG. 14B, the name of a tag including information aplurality of chapters of content may be the same as that of a tagdefining a plurality of media data. In other words, the tag defining aplurality of media data, i.e., a “Representation” tag, may be used todefine the plurality of chapters. Thus, each of “Period” tags definingreproduction periods, respectively, may include a “Representation” tagdefining media data in a corresponding reproduction period, and a“Representation” tag defining a plurality of chapters in thecorresponding reproduction period.

Referring to FIG. 14B, in a first “Period” tag, a first “Representation”tag is used to define media data, e.g., video data, and a second“Representation” tag is used to define a plurality of chapters. Thesecond “Representation” tag defines the “mimeType” attribute, the“width” attribute, the “height” attribute, and the “ImageInterval”attribute described above with reference to FIG. 14A so as to define aplurality of still images corresponding to the plurality of chapters.

As described above with reference to FIG. 14A, each of the“Representation” tags may include the “SegmentInfo” tag that is a lowertag defining a plurality of segments of the media data. Likewise, a“SegmentInfo” of the “Representation” tag of FIG. 14B, which defines theplurality of chapters, may define a plurality of segments divided from aplurality of still images according to a predetermined criterion. Theplurality of still images may be divided into a plurality of segmentsaccording to data size or time, and the plurality of segments may bedefined. As illustrated in FIG. 14B, each of the “SegmentInfo” tagsdefining the plurality of segments, respectively, may include “Url” tagssubject thereto, and each of the “URL” tags may define the URL of acorresponding still image.

FIG. 14C illustrates a case where a “Representation” tag defining aplurality of chapters does not include the “imageInterval” attribute. Asdescribed above, the plurality of chapters may be classified according ascene, or a story other than time. In this case, time intervals betweenstill images may not be uniform. Thus, as illustrated in FIG. 14C, the“Representation” tag may not include the “imageInterval” attribute, andmay define an “ImagePresentationTime” attribute in an “Url” tag includedin a “SegmentInfo” tag subject to the “Representation” tag. The“ImagePresentationTime” attribute defines time corresponding to a stillimage.

FIG. 14D illustrates a case where a plurality of still imagescorresponding to a plurality of chapters and time informationcorresponding to the plurality of still images are included in one file.Referring to FIG. 14D, a “chaptering.mp4” file includes not only aplurality of still images corresponding to a plurality of chapters butalso time information of each of the still images generated. The“chaptering.mp4” file may have a structure as will be later describedwith reference to FIG. 17 or may be generated in an ISO Base Media FileFormat (ISOBMFF).

A language based on which the “chaptering.mp4” file is generated isdefined with a “lang” attribute, and a method of reproducing informationregarding the plurality of chapters based on the “chaptering.mp4” fileis defined with a “contentviewpoint” attribute. If the“contentviewpoint” attribute is defined as “navigation”, then aplurality of still images included in the “chaptering.mp4” file arereproduced at a predetermined speed so that a user may select a stillimage corresponding to a desired point of time from among the pluralityof still images. Otherwise, the plurality of still images included inthe “chaptering.mp4” file may be displayed in a scrolling manner so thata user may select a still image among the plurality of still images thatare scrolled. A “mimeType” attribute defines the format of thechaptering.mp4″ file including the plurality of still images. If theformat of the “chaptering.mp4” file is “mp4”, then the “mimeType”attribute is defined as “jpeg/mp4” since the “chaptering.mp4” fileincludes the plurality of still image.

FIG. 14E illustrates a case where a plurality of files are generated,including information regarding a plurality of chapters, according to anembodiment. Location information of the plurality of files is definedwith a “sourceURL” attribute included in a “Url” tag.

As described above, one media data may be divided into a plurality ofsegments according to time. In this case, a file containing informationregarding chapters corresponding to the plurality of segments may be asillustrated in FIG. 14E. For example, from among the plurality ofsegments, still images belonging to a plurality of chapters included ina first segment may be included in a “seg-1.mp4” file, and still imagesbelonging to a plurality of chapters included in a second segmentreproduced after the first segment may be included in a “seg-2.mp4”file. A “mimeType” attribute and a “contentviewpoint” attribute are asdescribed above with reference to FIG. 14D.

FIG. 14F illustrates a case where times corresponding to the pluralityof files of FIG. 14E, respectively, are specified, according to anembodiment. Referring to FIG. 14F, the times corresponding to the filesthat include information regarding a plurality of chapters,respectively, are defined with an “imagePresentationTime” attribute.Referring to FIG. 14F, chapter information regarding media data from“00:00:00” to “00:20:00” is included in a “seg-1.mp4” file, and chapterinformation regarding media data from “00:20:00” to “00:40:00” isincluded in a “seg-2.mp4” file. If the files including the informationregarding the plurality of chapters correspond to a plurality of mediadata corresponding to different times, respectively, and times coveredby the files are not periodic, then the “imagePresentationTime”attribute may be used to define the starting times of the files,respectively, as illustrated in FIG. 14F.

FIG. 14G illustrates a case where information regarding a plurality ofchapters is included in one file. Compared to the case of FIG. 14D, a“Representation” tag defining a plurality of media data is used todefine a plurality of chapters, instead of a separate tag representingchapter information. When the size of the information regarding theplurality of chapters is not large and there is no need to generate aplurality of files, unlike in FIGS. 14E and 14F, the informationregarding the plurality of chapters may be completely included in onefile and the file may be defined using the “Representation” tag.

FIG. 14H illustrates a case where each of the “Url” tags of FIG. 14Cincludes attributes defining a language, a title, and a descriptionregarding a corresponding chapter, according to an embodiment. The titleand description of a still image corresponding to each of a plurality ofchapters are defined with a “title” attribute and a “description”attribute, respectively. The “title” attribute and the “description”attribute of each language defined by a “lang” attribute may be defined.If a “contentviewpoint” attribute is defined as ‘chapter’ unlike inFIGS. 14D to 14G, then still images corresponding to the plurality ofchapters are displayed in a thumbnail manner and a user may select oneof the displayed still images.

FIGS. 15A and 15B illustrate schemas of a chapter according to exemplaryembodiments. FIG. 16 illustrates information regarding a chapteraccording to the schemas of FIGS. 15A and 15B, according to anembodiment.

Referring to FIGS. 15A and 15B, information regarding a plurality ofchapters included in a media presentation description may be producedaccording to the schemas illustrated in FIGS. 15A and 15B. Specifically,referring to FIG. 16, a plurality of chapters of content may be definedwith a “ChapterItems” tag and a “ChapterItem” tag included in a“ChapterInfo” tag.

The “ChapterItem” tag defines a plurality of still images correspondingto the plurality of chapters. An identifier and time corresponding toeach of the still images are defined with an “id” attribute and a “time”attribute, respectively. The title and description of each of thechapters are defined as a “title” tag and a “Description” tag which arelower tags, respectively. A brief description of each of the chapter isdefined with a “Tag” tag. The “title” tag, the “Description” tag, andthe “Tag” tag are defined in a string, and the total number of stringsis not limited. A “lang” attribute defines a language used in each ofthe “title”, “Tag”, and “Description” tags. Referring to FIG. 15A, the“lang” attribute may be subject to each of the “title”, “Tag”, and“Description” tags or may be on a same level as the “title”, “Tag”, and“Description” tags. If the same language is used in the “title”, “Tag”,and “Description” and the tags are the same, then the “lang” attributedoes not need to be subject to the “title”, “Tag”, and “Description”tags, and may on the same level as the “title”, “Tag”, and “Description”tags and define a language used in “title”, “Tag”, and “Description”tags.

The “ChapterItems” tag includes a plurality of “ChapterItem” tags, anddefine the resolutions of the still images by using an “imgWidth”attribute and an “imgHeight” attribute. A common part of the URLS of thestill images is defined with a “ThumbnailImgUrlTemplate” attribute. TheURL of a still image may be determined by using the identifier of thestill image defined in the “id” attribute of the “ChapterItem” tag,instead of a “$ID$” of a URL template defined with the“ThumbnailImgUrlTemplate” attribute.

The media presentation description received in operation 1320 mayinclude a tag defining a plurality of media data and a tag includinginformation regarding a plurality of chapters as illustrated in FIG. 16.Also, an additional XML file produced according to the schemas of FIGS.15A and 15B may be transmitted or received separately from the mediapresentation description, in operation 1320. In other words, the client130 may request the server 120 to provide an XML file producedseparately from the media presentation description to include theinformation regarding the plurality of chapters according to the schemasof FIGS. 15A and 15B, and the server 120 may transmit the XML file tothe client 130.

Referring back to FIG. 13A, in operation 1330, the client 130 requeststhe server 120 provide chaptering data, and receives the chaptering datafrom the server 120. The chaptering data may be data regarding stillimages corresponding to a plurality of chapters of content that is beingstreamed. The client 130 may transmit an HTTP request for the chapteringdata to the server 120, and receive the chaptering data as a HTTPresponse.

The media presentation description received in operation 1320 includesthe URLs of the still images corresponding to the plurality of chaptersas described above. The client 130 requests the server 120 to providethe chaptering data based on the URLs, and receive the chaptering dataas a reply to the request. The chaptering data may include dataregarding the still images corresponding to the plurality of chapters ofthe content. The chaptering data will now be descried in detail withreference to FIG. 17.

FIG. 17 is a diagram illustrating the structure of chaptering data 1700according to an embodiment. Referring to FIG. 17, the chaptering data1700, such as chaptering data received in operation 1330, includes aheader 1710 and a plurality of still image data 1720. The header 1710includes still image number information 1712, still image time intervalinformation 1714, and still image data offset information 1716 and 1718included in the chaptering data 1700. The still image number information1712 defines the total number of still images included in the chapteringdata 1700. The still image time interval information 1714 defines timeintervals between the still images.

The still image data offset information 1716 and 1718 define offsets forspecifying still images 1722 and 724 from among the plurality of stillimage data 1720, respectively. The first still image 1722, i.e., “Jpg1”, is defined by the first still image data offset information 1716,and the second still image, i.e., “Jpg 2”, is defined by the secondstill image data offset information 1718. An absolute data intervalbetween the start of the plurality of still image data 1720 andspecified still image data may be defined with an offset.

Referring back to FIG. 13A, in operation 1340, the client 130 receivingthe chaptering data in operation 1330 requests the server 120 totransmit at least one media data from among the plurality of media data.The client 130 may select at least one media data encoded to have aquality sufficient for a current streaming environment from among theplurality of media data, based on the information regarding theplurality of media data, and then requests the server 120 to transmitthe selected media data. Also, the client 130 may transmit an HTTPrequest for predetermined media data to the server 120. Then the server120 transmits the at least one media data to the client 130 in responseto the request. The server 120 may encode the content to have apredetermined quality, divides the encoded content into several segmentsaccording to time, and transmit at least one of the segments to theclient 120. The server 120 may transmit the predetermined media data tothe client 130 as a HTTP response.

As described above with reference to FIGS. 5B and 11B, a header of atleast one media data selected adaptively to a streaming environment isfirst received and then the at least one media data may be received.

If the client 130 selects a particular chapter based on the chapteringdata received in operation 1330, at least one media data encoded to havea quality sufficient for the streaming environment is received, startingfrom the selected chapter. If the still images included in thechaptering data are displayed on a display device (not shown) of theclient 130 and a user selects a particular chapter, then data streamingmay be performed starting from the selected chapter. If a user of theclient 130 selects a particular chapter based on the chaptering dataduring streaming of the content, the client 130 may receive at least onemedia data, starting from the selected chapter.

FIG. 13B is a flowchart illustrating a streaming method according toanother embodiment. In FIG. 13B, operations 1312 and 1322 correspond tooperations 1310 and 1320 of FIG. 13A, respectively. In operation 1312,the client 130 requests the server 120 to provide information regardingcontent, and receives the information regarding the content, whichincludes the URL of a media presentation description, from the server120. In operation 1322, the client 130 requests the server 120 provide amedia presentation description including information regarding aplurality of chapters, based on the information regarding contentreceived in operation 1312, and then receives the media presentationdescription from the server 120.

In operations 1332 and 1342, the client 130 receives the chaptering databased on the information regarding the plurality of media data receivedin operation 1322, i.e., the information regarding the plurality ofchapters included in the media presentation description.

Specifically, in operation 1332, the client 130 may request the server120 to provide a header of the chaptering data, and receive the headerof the chaptering data from the server 120. As described above withreference to FIG. 17, the chaptering data 1700 may include the header1710 and the plurality of still image data 1720. In operation 1332, theclient 130 may request the server 120 to provide the header 1710 of thechaptering data 1700, and receive the header 1710 from the server 120.Since the header 1710 includes the still image number information 1712,the still image time interval information 1714, and the still image dataoffset information 1714 and 1716, the client 130 may request and receivethe plurality of still image data 1720, based on the header 1710, inoperation 1342.

In FIG. 13B, operation 1352 corresponds to operation 1340 of FIG. 13A.In operation 1352, the client 130 requests the server 120 to transmit atleast one media data from among the plurality of media data, andreceives the at least one media data from the server 120. In this case,when a user of the client 130 selects a particular chapter based on thechaptering data received in operations 1332 and 1342, the client 130 mayreceive at least one media data, starting from the selected chapter.

FIG. 18A is a flowchart illustrating a streaming method according toanother embodiment. Referring to FIG. 18A, in operation 1810, the client130 requests the server 120 to transmit information regarding aplurality of media data. The client 130 may transmit an HTTP request fora media presentation description to the server 120, and receive themedia presentation description from the server 120 as a HTTP response.The streaming method of FIG. 18A is different from the streaming methodof FIG. 13A in that the information regarding the plurality of mediadata is requested and received without requesting and receivinginformation regarding content. The media presentation descriptionreceived in operation 1810 may be the media presentation descriptionsillustrated in FIGS. 14A to 14H.

In operation 1820, the client 130 requests the server 120 to transmitchaptering data, and receives the chaptering data from the server 120.The chaptering data may be received based on the information regardingthe plurality of chapters included in the media presentation descriptionreceived in operation 1810.

In operation 1830, the client 130 requests the server 120 to transmit atleast one media data from among the plurality of media data. The client130 may select at least one media data encoded to have a qualitysufficient for a streaming environment from among the plurality of mediadata, based on the information regarding the plurality of media data,request the server 120 to transmit the at least one media data, and thenreceive the at least one media data from the server 120. If a particularchapter is selected based on the chaptering data received in operation1820, at least one media data may be requested and received, startingfrom the selected chapter.

As described above with reference to FIGS. 5B and 11B, a header of atleast one media data selected adaptively to a streaming environment mayfirst be received and the at least one media data may then be received.

FIG. 18B is a flowchart illustrating a streaming method according toanother embodiment. In FIG. 18B, operation 1812 corresponds to operation1810 of FIG. 18A. In operation 1812, the client 130 requests the server120 to transmit information regarding a plurality of media data. Theclient 130 may transmit an HTTP request for a media presentationdescription to the server 120 and receive the media presentationdescription from the server 120 as HTTP response. The streaming methodof FIG. 18B is different from the streaming method of FIG. 13B in thatthe information regarding the plurality of media data is requested andreceived without requesting and receiving information regarding content.The media presentation description received in operation 1812 may be themedia presentation descriptions illustrated in FIGS. 14A to 14H.

In operation 1822, the client 130 may request the server 120 to transmita header of chaptering data and receive the header of chaptering datafrom the server 120. In operation 1822, the client 130 may first requestthe server 120 to transmit the header 1710 of the chaptering data 1700of FIG. 17 and receive the header 1710 from the server 120. After theclient receives the header 1710 in operation 1822, the client mayrequest and receive the plurality of still image data 1720 based on theheader 1710, in operation 1832.

Operation 1842 corresponds to operation 1830 of FIG. 18A. In operation1842, the client 130 requests the server 120 to transmit at least onemedia data from among the plurality of media data, based on thechaptering data received in operations 1822 and 1832, and receives theat least one media data from the server 120. If a particular chapter isselected based on the chaptering data received in operations 1822 and1832, at least one media data may be requested and received, startingfrom the selected chapter.

FIG. 19 is a block diagram of a media data transmitting apparatus 1900that may be included in the server 120 of FIG. 1, according to anembodiment. Referring to FIG. 19, the media data transmitting apparatus1900 includes an information transmission or transmitting unit 1910 anda media data transmission or transmitting unit 1920.

The information transmission unit 1910 receives a request forpredetermined information from the client 130 and transmits therequested information to the client 130. The information transmissionunit 1910 may receive a request for at least one piece from amonginformation regarding content and information regarding a plurality ofmedia data from the client 130, and transmit the requested informationto the client 130. The information transmission unit 1910 may receive anHTTP request for at least one from among the information regarding thecontent and the information regarding the plurality of media data fromthe client 130, and transmit the requested information to the client 130as HTTP response.

The information regarding the plurality of media data that theinformation transmission unit 1910 transmits to the client 130 may be amedia presentation description. The media presentation description maybe as described above with reference to FIGS. 9A to 9H and 14A to 14H.Thus, as described above with reference to FIGS. 14A to 14H, the mediapresentation description may include information regarding a pluralityof chapters of content that is being streamed.

The media data transmission unit 1920 receives a request for at leastone media data, which is selected adaptively to a streaming environmentfrom among the plurality of media data, from the client 130, andtransmits the requested media data to the client 130. The media datatransmission unit 1920 may receive a request for at least one mediadata, which is selected based on the media presentation description thatthe information transmission unit 1910 transmits to the client 130, fromthe client 130. The server 120 may receive a plurality of media data,which are encoded to have different qualities, respectively, from theencoding device 110, store the plurality of media data, and transmit atleast one media data requested to the client 130 from among the storedmedia data. Otherwise, the server 120 may receive media data from theencoding device 110 and transmit the media data to the client 130 inreal time, in response to a request from the client 130.

As described above with reference to FIGS. 13A, 13B, 18A, and 18B, theclient 130 may request chaptering data based on the media presentationdescription that includes the information regarding the plurality ofchapters. Then, the media data transmission unit 1920 may transmit thechaptering data to the client 130. When the client 130 requests at leastone media data corresponding to a particular chapter, based on thechaptering data, the media data transmission unit 1920 may transmit atleast one media data to the client 130, starting from the particularchapter.

The client 130 may select a chapter during streaming of content, and inthis case, the streaming is stopped and at least one media data istransmitted to the client 130, starting from the selected chapter.

The media data transmission unit 1920 may transmit the entire chapteringdata to the client 130 at a time, as illustrated in FIGS. 13A and 18A,or may first transmit a header of the chaptering data and then transmitstill image data as illustrated in FIGS. 13B and 18B.

FIG. 20 is a diagram of a media data receiving apparatus 2000 that maybe included in the client 1300 of FIG. 1, according to an embodiment.Referring to FIG. 20, the media data receiving apparatus 2000 of theclient 130 includes an information receiving unit 2010 and a media datareceiving unit 2020.

The information receiving unit 2010 transmits a request for desiredinformation to the server 120, and receives the requested informationfrom the server 120. A request for at least one from among informationregarding content and information regarding a plurality of media datamay be transmitted to the server 120 and may be received from the server120. According to the embodiment of one of FIGS. 2A, 2B, 5A, 5B, 11A,11B, 13A, 13B, 18A, and 18B, an HTTP request for at least one from amongthe information regarding the content and the information regarding theplurality of media data may be transmitted to the server 120 and the atleast one information may be received from the server 120 as a reply tothe HTTP request.

The information regarding the plurality of media data that the server120 transmits to the client 130 may be a media presentation description.The media presentation description may be as described above withreference to FIGS. 9A to 9H and 14A to 14H. Accordingly, the mediapresentation description may include information regarding a pluralityof chapters of content that is being streamed, as described above withreference to FIGS. 14A to 14H.

The media data receiving unit 2020 transmits a request for at least onemedia data selected according to a streaming environment from among theplurality of media data, to the server 120, and receives the requestedmedia data from the client 130. The media data receiving unit 2020 maytransmit the request for the selected media data to the server 120,based on the information regarding the plurality of media data that theinformation receiving unit 2010 receives from the server 120.

The media data receiving unit 2020 may request content sufficient forthe streaming environment, based on the media presentation descriptionreceived from the server 120. The media presentation descriptionincludes information regarding the plurality of chapters as describedabove. Thus, the media data receiving unit 2020 may request and receivechaptering data, based on the media presentation description. The mediadata receiving unit 2020 may select a chapter based on the chapteringdata, and may request the server 120 to provide media data correspondingto the selected chapter server 120. The media data receiving unit 2020may receive the entire chaptering data from the server 120 at a time asillustrated in FIGS. 13A and 18A, or may first receive a header of thechaptering data and then receive still image data as illustrated inFIGS. 13B and 18B.

According to the above embodiments, it is possible to stream media dataregarding content having a plurality of chapters, adaptively accordingto a streaming environment.

While the inventive concept has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the inventive concept as defined by the following claims.

A system according to an embodiment can also be embodied as computerreadable codes on a computer readable recording medium.

For example, a streaming apparatus of a server and a streaming apparatusof a client may include a bus coupled to each unit of the apparatuses1900 and 2000 of FIGS. 19 and 20, and at least one processor connectedto the bus. Also, the streaming apparatuses may further include a memorythat is coupled to the bus so as to store a command, a received message,or a generated message and that is coupled to the at least one processorso as to perform commands as described above.

The computer readable recording medium may be any recording apparatuscapable of storing data that is read by a computer system. Examples ofthe computer readable recording medium include read-only memory (ROM),random-access memory (RAM), CD-ROMs, magnetic tapes, floppy disks,optical data storage devices, etc. The computer readable recordingmedium can also be distributed over network coupled computer systems sothat the computer readable code is stored and executed in a distributedfashion.

What is claimed is:
 1. A method of receiving media data in a client, themethod comprising: receiving from a server, a file comprisinginformation regarding a plurality of media data having differentqualities, and at least one of information associated with a pluralityof a chapters of content, the different qualities of the plurality ofmedia data being generated by encoding data by applying differentencoding settings to the same content and dividing the encoded databased on time; selecting, by the client, first media data from among theplurality of media data based on the received file; transmitting arequest for the first media data; and receiving, from the server, thefirst media data in response to the request, identifying chapterinformation based on the received file; transmitting a request forsecond media data based on the identified chapter information; andreceiving, from the server, the second media data associated with theidentified chapter information, wherein, if the second media data havinga second quality is requested while the first media data having a firstquality, different from the second quality, is transmitted, time stampsof the first media data and the second media data are continuouslyaligned so that the first media data and the second media data arecontinuously reproduced.
 2. The method of claim 1, wherein the contentis divided into the plurality of chapters and the received file furthercomprises information regarding a plurality of still imagescorresponding to each of the plurality of chapters of the content, andwherein the receiving of the second media data comprises: receiving theplurality of still images, based on the received file; and receiving thesecond media data, starting from a chapter selected based on theplurality of still images.
 3. The method of claim 2, wherein theinformation regarding the plurality of still images comprises a firsttag which comprises at least one from among location information,resolution information, and compression type information regarding theplurality of still images.
 4. The method of claim 3, wherein the firsttag and a second tag that identifies a reproduction period of thecontent are at a same level.
 5. The method of claim 3, wherein the firsttag and a third tag that is subject to a second tag that identifies areproduction period of the content, and that defines a plurality ofmedia data to be reproduced in a predetermined reproduction period areat a same level.
 6. The method of claim 3, wherein the first tag furthercomprises information regarding intervals between the plurality of stillimages.
 7. A non-transitory computer readable recording medium havingstored thereon a computer readable program which when executed by acomputer performs the method of claim
 1. 8. The method of claim 1,wherein the receiving of the first media data comprises: estimating, bythe client, a streaming environment based on at least one of a timestamp and a bit error rate of currently received media data; selecting,by the client, the first media data that has a quality corresponding tothe estimated streaming environment; and receiving, by the client, theselected first media data.
 9. The method of claim 1, wherein the contentis divided into the plurality of chapters, and wherein, if the secondmedia data is requested while the first media data is transmitted,transmission of the second media data is performed following the firstmedia data, starting from a corresponding chapter.
 10. A method oftransmitting media data, the method comprising: transmitting to aclient, a file comprising information regarding a plurality of mediadata generated by encoding content, and at least one of informationassociated with a plurality of a chapters of the content, the pluralityof media data having different qualities, and the different qualities ofthe plurality of media data being generated by applying differentencoding settings to the same content; receiving, from the client, arequest for first media data from among the plurality of media dataselected based on the transmitted file; transmitting the first mediadata to the client, in response to the request received from the client,receiving, from the client, a request for second media data based onchapter information that is identified based on the transmitted file;and transmitting the second media data associated with the identifiedchapter information, wherein, if the second media data having a secondquality is requested while the first media data having a first quality,different from the second quality, is transmitted, time stamps of thefirst media data and the second media data are continuously aligned sothat the first media data and the second media data are continuouslyreproduced.
 11. The method of claim 10, wherein the content is dividedinto the plurality of chapters and the transmitted file furthercomprises information regarding a plurality of still imagescorresponding to each of the plurality of chapters of the content, andwherein the transmitting of the second media data to the clientcomprises: transmitting the plurality of still images to the client, inresponse to the request based on the transmitted file, received from theclient; and transmitting the second media data, starting from a chapterselected by the client based on the plurality of still images.
 12. Themethod of claim 11, wherein the information regarding the plurality ofstill images comprises a first tag which comprises at least one fromamong location information, resolution information, and compression typeinformation regarding the plurality of still images.
 13. The method ofclaim 12, wherein the first tag and a second tag that identifies areproduction period of the content are at a same level.
 14. The methodof claim 12, wherein the first tag and a third tag that is subject to asecond tag, which identifies a reproduction period of the content, andthat defines a plurality of media data to be reproduced in apredetermined reproduction period are at a same level.
 15. The method ofclaim 12, wherein the first tag further comprises information regardingintervals between the plurality of still images.
 16. A non-transitorycomputer readable recording medium having stored thereon a computerreadable program which when executed by a computer performs the methodof claim
 10. 17. The method of claim 10, wherein the receiving of thefirst media data comprises: estimating, by the client, a streamingenvironment based on at least one of a time stamp and a bit error rateof currently received media data; selecting, by the client, the firstmedia data that has a quality corresponding to the estimated streamingenvironment; and receiving, by the client, the selected first mediadata.
 18. The method of claim 10, wherein the content is divided intothe plurality of chapters, and wherein, if the second media data isrequested while the first media data is transmitted, transmission of thesecond media data is performed following the first media data, startingfrom a corresponding chapter.
 19. An apparatus for receiving media data,the apparatus comprising: an information receiving unit which receivesfrom a server, a file comprising information regarding a plurality ofmedia data generated by encoding content, and at least one ofinformation associated with a plurality of a chapters of the content,the plurality of media data having different qualities, and thedifferent qualities of the plurality of media data being generated byapplying different encoding settings to the same content; and a mediadata transceiving unit which transmits a request for first media datafrom among the plurality of media data selected based on the receivedfile and a request for second media data based on identified chapterinformation, and which receives, from the server, the first media datain response to the request for the first media data and the second mediadata associated with the identified chapter information in response tothe request for the second media data, wherein, if the second media datahaving a second quality is requested while the first media data having afirst quality, different from the second quality, is transmitted, timestamps of the first media data and the second media data arecontinuously aligned so that the first media data and the second mediadata are continuously reproduced.
 20. The apparatus of claim 19, whereinthe media data transceiving unit estimates a streaming environment basedon at least one of a time stamp and a bit error rate of currentlyreceived media data and selects the plurality of the first media datahaving a quality corresponding to the estimated streaming environment.21. The apparatus of claim 19, wherein the content is divided into theplurality of chapters, and wherein, if the second media data isrequested while the first media data is transmitted, transmission of thesecond media data is performed following the first media data, startingfrom a corresponding chapter.
 22. An apparatus for transmitting mediadata, the apparatus comprising: an information transmitting unit whichtransmits to a client, a file comprising information regarding aplurality of media data generated by encoding content, and at least oneof information associated with a plurality of a chapters of the content,the plurality of media data having different qualities, and thedifferent qualities of the plurality of media data being generated byapplying different encoding settings to the same content; and a mediadata transceiving unit which receives a request for first media datafrom among the plurality of media data selected based on the transmittedfile and a request for second media data based on chapter informationthat is identified based on the transmitted file, and which transmits,to the client, the first media data in response to the request for thefirst media data and the second media data associated with theidentified chapter information in response to the request for the secondmedia data, wherein, if the second media data having a second quality isrequested while the first media data having a first quality, differentfrom the second quality, is transmitted, time stamps of the first mediadata and the second media data are continuously aligned so that thefirst media data and the second media data are continuously reproduced.23. The apparatus of claim 22, wherein the media data transceiving unitestimates a streaming environment based on at least one of a time stampand a bit error rate of currently received media data and selects thefirst media data having a quality corresponding to the estimatedstreaming environment.
 24. The apparatus of claim 22, wherein thecontent is divided into the plurality of chapters, and wherein, if thesecond media data is requested while the first media data istransmitted, transmission of the second media data is performedfollowing the first media data, starting from a corresponding chapter.